The present invention relates generally to the treatment of stormwater and similar surface runoff. More particularly, the present invention relates to the removal of floatable and non-floatable matter there from so that cleaner water is returned to the environment.
Eighty percent of the pollution to the North American fresh water resource has been attributed to stormwater runoff. Sediments, contaminated by hydrocarbons and their floating residuals, flow freely from paved impervious sites into storm water collection systems. Mitigated wetlands and storm water ponds are historically accepted as the method of controlling storm water quality. While ponds and wetlands are, on one hand, an effective treatment for non-point source discharges, they nevertheless undesirably occupy valuable commercial property and create an open water liability.
Oil and grit separators have been used to control hydrocarbon loadings. Such a separator comprises a concrete structure linked to the storm drain system with two pools used to trap oil and grit. Such a separator is illustrated in xe2x80x9cHydrocarbon Hotspots in the Urban Landscape: Can they be Controlled?xe2x80x9d Watershed Protection Techniques, Vol. 1, No. 1, February, 1994. This article states that recent research indicates that such oil and grit separators are not effective in trapping pollutants.
U.S. Pat. No. 5,759,415 describes a storm water treatment system which has a tangential inlet to a circular grit chamber wherein a swirling motion is produced to direct settleable solids toward the center and to reduce resuspension in the grit chamber. The water is released from the grit chamber into an oil chamber defined between the grit chamber and a barrier wall, which has an outlet that is located at the bottom thereof to thereby provide a baffle that traps floatables in the oil chamber. The barrier wall also has an upper overflow outlet. These outlets direct the water into a flow control chamber that has a lower outlet higher than the lower outlet from the oil chamber and has upper overflow outlet. These flow control chamber outlets, which are provided with weirs for flow control, direct the water into an outlet chamber from which the treated water is removed through a lower outlet pipe.
According to the ""415 patent, the grit chamber outlet is in the wall thereof Thus, water swirling along the side of the circular grit chamber wall is passed through this outlet. Suspended particulate matter may not have been adequately removed from this water by the time it passes into the outlet that is also inefficiently large in size. It is therefore considered desirable to more efficiently remove particulate matter from the water before it is passed into the oil chamber.
It is accordingly an object of the present invention to provide a more efficient storm water treatment system.
It is also an object of the present invention to provide such a system which is inexpensive, easy to operate, and reliable.
In order to provide such a system, in accordance with the present invention, runoff water is passed tangentially into a primary chamber wherein non-floatable matter is removed by swirling action of the water, then through an outlet for passage into a secondary chamber for removal of oil and other floatable matter therefrom, the outlet being located centrally of the primary chamber to remove water from which greater amounts of non-floatable matter has been removed.
The outlet from the primary chamber is preferably provided by a conduit that extends into the primary chamber with its end portion, which provides the outlet, disposed vertically.
The above and other objects, feature, and advantages of the present invention will be apparent in the following detailed description of the preferred embodiment thereof when read in conjunction with the appended drawings wherein the same reference numerals denote the same or similar parts throughout the several views.